Cooling system and cooling method

ABSTRACT

A cooling system comprising an evaporation cooling device for evaporating an aqueous solution, a water content providing device for allowing vapor evaporated from impurities-containing water to be absorbed into the aqueous solution, and a circulating device for circulating the aqueous solution between the water content providing device and the evaporation cooling device; and a cooling method characterized by comprising the steps of taking in impurities-containing water, cooling a high-temperature body by evaporating water content in an aqueous solution having a boiling point higher than that of the impurities-containing water, allowing vapor evaporated from the impurities containing water to be absorbed into the aqueous solution concentrated by the cooling step, feeding the aqueous solution diluted in the absorbing step to the cooling step, and discharging the impurities-containing water concentrated in the absorbing step. The aqueous solution circulates between the water content providing device and the aqueous solution desalination device, and no salts move between the aqueous solution and the impurities-containing water, thereby providing a cooling system free from scales.

TECHNICAL FIELD

The present invention relates to a cooling system which utilizesevaporation latent heat of water and a cooling method.

BACKGROUND ART

Water has large evaporation latent heat, and is used for cooling byevaporation, for a distillation device, a generation system, a heatengine, or a cooling device. There have been a problem, however, suchthat scale originated from impurities contained in the water adheres toan evaporation part due to condensation of water, when the watercontaining the impurities is caused to be evaporated. Therefore, workfor removing scale is required frequently. In particular, usage ofseawater having the impurities that cause hard scale gives rise toproblems in the cooling by evaporation.

The present invention is made in view of the above, an object of thepresent invention is to provide a novel cooling system and a coolingmethod, in which adhesion of scale accompanied by evaporation isreduced.

DISCLOSURE OF INVENTION

According to an embodiment of the present invention, a novel coolingsystem is provided, which includes an evaporation cooling device whichevaporates aqueous solution having a higher boiling point than that ofimpurities-containing water, a water providing device which causes watervapor evaporated from the impurities-containing water to be absorbed inthe aqueous solution, and a circulation device which circulates theaqueous solution between the water providing device and the evaporationcooling device.

As the impurities-containing water, water containing salts or organicmaterials which are the origin of scale-generation may be used, such aspurified water, river water, lake water, groundwater, seawater, or wastewater.

The aqueous solution is a kind of water having a molar elevation ofboiling point higher than that of the impurities-containing water. Theaqueous solution may include salts having large solubility, such assodium chloride, sodium magnesium, sodium calcium, or the like, assolute.

A permeating member which permeates the aqueous solution may be providedon an evaporation surface where the aqueous solution evaporates. Thecooling system may further include a sprinkler which sprinkles theevaporation surface with the aqueous solution.

The cooling system may further include a dust prevention device forpreventing adhesion of dust of the air to the evaporation surface.

The cooling system may further include a device for enhancingevaporation of the aqueous solution, for example, a ventilator or achimney.

With the above-mentioned evaporation of the aqueous solution, theaqueous solution is concentrated due to loss of water. Theabove-mentioned water providing device causes water vapor evaporatedfrom the impurities-containing water to be absorbed in the aqueoussolution. The aqueous solution which is concentrated is therebyreplenished with water.

The water providing device may be an absorption heat pump which issupplied with the impurities-containing water and the aqueous solution.In this case, the cooling system may further include a heating devicefor operating the absorption heat pump in a high-temperature atmosphere.Alternatively, the cooling system may further include a vacuum devicefor operating absorption heat pump in a vacuum atmosphere.

In order to prevent adhesion of solid materials included in theimpurities-containing water to the water providing device, a filtrationdevice for removing the solid materials may be provided for the coolingsystem. Further, the cooling system may further include a waterprocessing device which decomposes organic materials contained in theimpurities-containing water.

When the cooling system further includes a distillation device having acondensation part, and distills saline water or the like, theevaporation cooling device is disposed at the condensation part. Thedistillation device may further include a heat-absorbing surface forabsorbing thermal energy of the atmosphere. The distillation device mayperform distillation, under supply of solar thermal energy.

When the cooling system further includes a steam power generating systemhaving a condenser, and generates electricity, the evaporation coolingdevice is disposed at the condenser.

When the cooling system further includes an internal combustion engine,and generates power, the evaporation cooling device is disposed at theinternal combustion engine.

When the cooling system includes an air conditioner having a hightemperature heat source, the evaporation cooling device is disposed forcooling the high temperature heat source. When the water supply/drainagesystem is installed in a region crowded with the air conditioners, aheat-island phenomenon of the region is relaxed.

According to another embodiment of the present invention, a coolingmethod is provided, which includes the steps of, takingimpurities-containing water, cooling a high-temperature body byevaporating water of an aqueous solution having a boiling point higherthan that of the impurities-containing water, causing the water vaporevaporated from the impurities-containing water to be absorbed in theaqueous solution concentrated by the cooling step, sending the aqueoussolution diluted by the absorption step to the cooling step, anddraining the impurities-containing water concentrated by the absorptionstep.

The absorption step may be performed using an absorption heat pump whichis supplied with the impurities-containing water and the aqueoussolution. In order to operate the absorption heat pump at ahigh-temperature, the cooling method may further include a heating stepfor heating the impurities-containing water. Alternatively, the coolingmethod may further include a vacuum evacuating step for operating theabsorption heat pump in a vacuum atmosphere.

The cooling method may further include a step for ventilating anevaporation surface of the aqueous solution, in order to enhanceevaporation of the aqueous solution in the cooling step.

The cooling method may further include a dust removing step forpreventing adhesion of dust of the air to the evaporation surface.

The cooling method may further include a step for removing solidmaterials contained in the impurities-containing water or a step fordecomposing organic materials contained in the impurities-containingwater.

The cooling method may further include a step for adding a biologicalpropagation prevention agent to the aqueous solution.

A value of molar elevation of boiling point of the aqueous solution isincreased due to condensation accompanied by the evaporation of theaqueous solution. In dealing with this, the aqueous solution before thecondensation may be supplied to a low-temperature part of theevaporation surface. In this case, the aqueous solution flows from thelow-temperature part of the evaporation surface of the aqueous solutionin the cooling step toward a high-temperature part.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual view illustrating a cooling system according toan embodiment of the present invention.

FIG. 2 is a conceptual view illustrating a part of a section of aplurality of absorption heat pumps arranged inside a water providingdevice used in the cooling system illustrated in FIG. 1.

FIG. 3 is a conceptual view illustrating a cooling system according toanother embodiment of the present invention.

FIG. 4 is a conceptual view illustrating a cooling system according tostill another embodiment of the present invention.

FIG. 5 is a conceptual view illustrating a cooling system according tostill another embodiment of the present invention.

FIG. 6 is a conceptual view illustrating a cooling system according tostill another embodiment of the present invention.

FIG. 7 is a conceptual view illustrating a section of an evaporationcooling device used in a cooling system according to still anotherembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to accompanying drawings, the present invention is explainedfor more detailed illustration of the present invention. The samereference numeral designates the same or corresponding part throughoutthe several views.

FIG. 1 is a conceptual view illustrating a cooling system according toan embodiment of the present invention. In FIG. 1, the cooling systemincludes an evaporation cooling device 10, a water providing device 20,and a circulation device 30 which circulates aqueous solution betweenthe water providing device 20 and the evaporation cooling device 10.

The circulation device 30 includes supply piping 31 and return piping33, and circulates the aqueous solution between the evaporation coolingdevice 10 and the water providing device 20. Water in the aqueoussolution is caused to be evaporated at the evaporation cooling device10. Because latent heat is absorbed by this evaporation of the aqueoussolution, the evaporation cooling device 10 cools a high-temperaturebody 100. Water vapor generated by this evaporation is ejected outsidethe system.

The aqueous solution concentrated by this evaporation due to loss ofwater is sent from the evaporation cooling device 10 to the waterproviding device 20 via the return piping 33.

The water providing device 20 is supplied with impurities-containingwater through a supply device 41. In the water providing device 20, thewater vapor evaporated from the impurities-containing water is absorbedin the aqueous solution. The aqueous solution which is caused to recoverwater by the absorption of water vapor is again sent to the evaporationcooling device 10 via the supply piping 31. Continuous evaporationcooling is thereby performed. The impurities-containing waterconcentrated in the water providing device 20 due to loss of water isdrained outside the system by a draining device 43.

The water providing device 20 includes an absorption heat pump. In thiscase, the aqueous solution includes solute and water as a solvent.Therefore, the aqueous solution has a boiling point higher than that ofthe pure water. The solute is a non-volatile material, and aconcentration of the solute is adjusted so that a value of molarelevation of boiling point of the aqueous solution exceeds the value ofmolar elevation of boiling point of the impurities-containing water. Asthe solute, a material having high-solubility; such as sodium chloride,sodium magnesium, sodium calcium, lithium bromide, ammonium chloride,and so forth, may be used.

Inside the water providing device 20 illustrated in FIG. 1, a pluralityof absorption heat pumps are arranged in series. FIG. 2 is a conceptualview illustrating a part of the serial arrangement. The number of unitsof the absorption heat pumps 50 in the arrangement is optional. Thearrangement may be arranged along a straight line. Alternatively, itmaybe arranged along a closed line.

One unit of the plurality of absorption heat pumps 50 includes a hightemperature heat source 51 which is supplied with the aqueous solutionand a refrigeration source 53 which is supplied with theimpurities-containing water. The high temperature heat source 51 and therefrigeration source 53 are disposed opposite each other via a gap, inwhich the water vapor evaporated from the impurities-containing waterexisting at the refrigeration source 53 is diffused toward the hightemperature heat source 51, and is absorbed in the aqueous solutionexisting at the high temperature heat source 51. Latent heat is releasedaccompanied by condensation of the water vapor at the high temperatureheat source 51, the latent heat accompanied by the evaporation of wateris derived from the refrigeration source 53. There is a heat conductingplate 55 between each high temperature heat source 51 in the arrangementand the refrigeration source 53 of the adjacent absorption heat pump,which improves heat transmittance between the high temperature heatsource 51 and the refrigeration source 53 of the adjacent heat pump 50.Namely, the heat released from the high temperature heat source 51 inthe arrangement is caused to be absorbed in the adjacent refrigerationsource via the heat conducting plate 55. In FIG. 2, this thermal energymoves from the left to the right. The heat conducting plate 55 hasnon-permeability, and separates the high temperature heat source 51 anda refrigeration source 53so that mixing or migration of salts is notcaused due to contact of the aqueous solution with theimpurities-containing water.

As the high temperature heat source 51 and the refrigeration source 53,a member which permeates the aqueous solution and theimpurities-containing water may be used. A kind of material thatpermeates water or saline water, such as sponge, woven cloth, non-wovencloth, paper, and so forth, may be used. Further, it may be a coatingmaterial having a pro-aqueous group, with which the heat conductingplate 55 is coated. Further, any material that permeates water, such assoil or charcoal, may be used. Further, the above permeating member orcoating material may be arranged along with an adequate pattern forperforming a good thermal transmitting property, for example, a stripedpattern.

According to the above-explained operation of the absorption heat pumps50, the impurities-containing water provides water for the evaporationcooling to the aqueous solution. As the impurities-containing water,seawater, groundwater containing salts, industrial waste water,household waste water, or purified water may be used, for example.

A guide for preferably operating the above-mentioned absorption heatpumps 50 is described as follows.

First, in increasing an amount of water transferred from theimpurities-containing water to the aqueous solution, the operation ofthe absorption heat pump 50 is generally performed near the boilingpoint of the impurities-containing water at the operational pressure.Therefore, a vacuum system is added for the operation in a vacuumatmosphere at a room temperature. Alternatively, the operationaltemperature may be raised by heating. In reducing energy consumption forthe heating, heat may be exchanged between the aqueous solution and theimpurities-containing water flowing into the water providing device 20and the aqueous solution and the impurities-containing water flowing outtherefrom. Because migration of materials through scattered water dropsdue to boiling is undesirable, the operational conditions are determinedtaking into account of this.

Second, when thermal conductivity by the heat conducting plate 55between the high temperature heat source 51 and the refrigeration source53 is high, the amount of water transferred from theimpurities-containing water to the aqueous solution increases.

Third, when a gap-length between the high temperature heat source 51 andthe refrigeration source 53 is short, the amount of water transferredfrom the impurities-containing water to the aqueous solution increases.In this case, because direct contact of the high temperature heat source51 with the refrigeration source 53 is undesirable, adequate gapmaintaining members may preferably be disposed in the gap.

Fourth, when increment of concentration of the drainedimpurities-containing water is small, the amount of water transferredfrom the impurities-containing water to the aqueous solution increases.Therefore, supply of the impurities-containing water with an adequateflow-rate and drainage thereof are preferred. In this case, an amount ofscale-precipitation at the refrigeration source is greatly reduced.

Fifth, when the concentration of the drained aqueous solution isreduced, the saturation pressure of the aqueous solution increases, andthe cooling capacity is improved.

Sixth, flowing out of the water vapor with the direction of thegap-plane, or the direction parallel to the plane of the heat conductingplate 55, reduces efficiency, a shield plate for preventing the flowingout may be disposed in a side part of the gap, if necessary.

FIG. 3 is a conceptual view illustrating an evaporation cooling systemaccording to another embodiment of the present invention. In addition tothe evaporation cooling system illustrated in FIG. 1, the evaporationcooling system illustrated in FIG. 3 further includes a sprinkler 60which sprinkles an evaporation surface with the aqueous solution. Aplurality of radiator-plates 11 are provided for the evaporation coolingdevice 10. According to the sprinkler, the cooling capacity of thecooling system is improved.

FIG. 4 is a conceptual view illustrating an evaporation cooling systemaccording to still another embodiment of the present invention. Inaddition to the evaporation cooling system illustrated in FIG. 1, theevaporation cooling system illustrated in FIG. 4 further includes aventilator 70 which ventilates an evaporation surface of the evaporationcooling device 10, a filtration device 91 which removes solid materialscontained in the impurities-containing water, and a filtration device 93which removes solid materials contained in the aqueous solution. Becauseevaporation is enhanced by the ventilator 70, the cooling capacity ofthe cooling system is improved. Further, the filtration device 91 andthe filtration device 93 prevent sedimentation of solid materials in thewater absorbing device 20.

FIG. 5 is a conceptual view illustrating an evaporation cooling systemaccording to still another embodiment of the present invention. Inaddition to the evaporation cooling system illustrated in FIG. 1, theevaporation cooling system illustrated in FIG. 5 further includes aheating device 80 which heats aqueous solution passing through thereturn piping 33 utilizing heat of the high-temperature body to becooled. The water providing device 20 includes the absorption heat pump.Further, a heat exchanger 81 which closes temperature difference betweenimpurities-containing water and the aqueous solution is provided for thewater providing device 20. Therefore, enhancement of the cooling of ahigh-temperature body and an amount of diffused water vapor in theabove-mentioned absorption heat pump are increased, and the coolingcapacity of the evaporation cooling system is improved.

FIG. 6 is a conceptual view illustrating an evaporation cooling systemaccording to still another embodiment of the present invention. In FIG.6, the cooling system includes a plurality of evaporation coolingdevices 10, a water providing device 20, and a circulation device 35which circulates aqueous solution between the water providing device 20and each of the evaporation cooling devices 10. The circulation device35 includes supply piping 31 and return piping 33. The water providingdevice 20 includes a water supplying device 41 and a water drainingdevice 43, and is supplied with impurities-containing water.

Each of the evaporation cooling devices 10 is connected to a heat sourceof an air conditioner (not shown). Temperature-rise in a region due to aheat-island phenomenon is eased, by disposing the circulation device 35in a prescribed region, and by connecting it to the air conditioner 10in the region. Further, because the evaporation cooling efficientlyreduces temperature of the high temperature heat source of theair-conditioner 10, saving energy is realized.

FIG. 7 is a conceptual view illustrating a section of an evaporationcooling device which is used in a cooling system according to stillanother embodiment of the present invention. In FIG. 7, the evaporationcooling device 10 is connected to a multi-effect distillation device101. The multi-effect distillation device includes a heat absorbingsurface 103, a solution-permeating member 105, and a condensationsurface 107. The heat absorbing surface 103 absorbs atmospheric thermalenergy and/or solar radiation. The solution-permeating member 105 issupplied with solution to be distilled.

The evaporation cooling device 10 and the multi-effect distillationdevice 101 are installed in the atmosphere. When humidity of theatmosphere is low, the temperature of the evaporation cooling device iscaused to be lower than the temperature of the atmosphere. Therefore,the multi-effect distillation device 101 can distill the solution evenif the solar radiation is not incident thereon. As the solution, theaqueous solution may be used. In this case, distilled water is obtained.

Hereinafter, an exemplary operation of the cooling system is explained.

This exemplary operation is made for illustrating the cooling system andthe cooling method more concretely, and is not described for limitingthe cooling system and the cooling method according to the presentinvention.

The exemplary operational condition, which is explained as follows, isthe operational condition in the cooling system illustrated in FIG. 1.As the water providing device 20, the plurality of absorption heat pumps50 having the structure illustrated in FIG. 2 are used. Aluminum havinga plate-thickness of 1 mm, in which corrosion resistance is improved byanode oxidation, is used as the heat conducting plate 55. As thematerial for the high temperature heat source and the refrigerationsource, thin cloth is used as the permeating body. The distance betweenthe high temperature heat source and the refrigeration source is set tobe 5 mm.

An arrangement of one block is constituted by serially arranging 1000units of absorption heat pumps 50. The water providing device 20includes a vacuum container having an evacuation system. Ten blocks ofthe arrangement of the absorption heat pumps are disposed in the vacuumcontainer for the water providing device 20. By a heat transmittingmeans consisting of another aluminum plate treated with the anodeoxidation treatment, a high temperature heat source at an edge portionof the block is thermally connected to a refrigeration source of theadjacent block. A content of the vacuum container is 100 m³.

Seawater is used as the impurities-containing water. A value of molarelevation of boiling point of the seawater is about 0.5° C. Sodiumchloride solution is used as the aqueous solution. A value of molarelevation of boiling point of the aqueous solution supplied to the waterproviding device 20 is set at 2.5° C. When a temperature of the seawateris below the temperature of the sodium chloride solution, a heatexchanging step is performed in advance so that the temperaturedifference is cause to be reduced. An operational pressure of the waterproviding device 20 is set near the saturated vapor pressure of theseawater at the operational temperature.

An amount of the aqueous solution supply is set so that a value of molarelevation of boiling point of the sodium chloride solution drained fromthe water providing device 20 is caused to be 1° C. An amount of theseawater supply is set so that a value of molar elevation of boilingpoint of the seawater drained from the water providing device is causedto be 0.6° C. When the value of molar elevation of boiling point of theseawater drained from the water providing device is high, namely, whenthe seawater is highly concentrated, an amount of scale precipitation inthe water providing device increases. If the scale is generated in thewater providing device, it is appropriately removed.

In the evaporation cooling device, the scale precipitation is greatlyreduced.

In reducing the present invention into practice, which is explained indetail in the above, an additional step may be performed for preferablyperforming he cooling method according to the present invention. Forexample, it is an oil-removing treatment, or removal of volatileelements and resolved gas and so forth. Further, a sterilizing treatmentsuch as an ozone treatment or an addition of chlorine may be performed.An antifungal treatment may be performed for the permeating member andso forth.

Besides, the present invention may be reduced into practice accompanyinga supplementary means for preferably operating the cooling system andthe cooling method according to the present invention, for example,coating for improving corrosion resistance, a surface treatment, atemperature sensor, monitoring of salts concentration, and so forth.

Accordingly, the present invention disclosed herein provides a novelcooling system and a cooling method, wherein in view of the teachingsdisclosed in the above-mentioned detailed explanation, a practice of thepresent invention is not limited to the above-mentioned examples forexplaining the preferred embodiments of the present invention, andwherein the present invention may be practiced as other embodiments withvariations within the scope of the claims as follows or may be practicedwithout supplementary forms or elements which are appended forexplaining the preferred embodiments.

Industrial Applicability

According to the cooling system and the cooling method of the presentinvention, a cooling system is realized, wherein there are no problemswhich arise from the scale. Further, because the cooling is efficientlyperformed, the cooling having reduced energy consumption is realized.The present invention is reduced into practice for a system such as asaline water desalination system, a generation system, an internalcombustion engine, or a heat pump, in which the cooling by evaporationof water is performed.

1. A cooling system, comprising: an evaporation cooling device forevaporating an aqueous solution having a boiling point higher than thatof an impurities-containing water; a water providing device which causeswater vapor evaporated from the impurities-containing water to beabsorbed in the aqueous solution, a circulation device which circulatesthe aqueous solution between the water providing device and theevaporation cooling device; and a distillation device having acondensation part, wherein the evaporation cooling device is disposed atthe condensation part.
 2. The cooling system according to claim 1,wherein the aqueous solution includes a sodium chloride as a solute. 3.The cooling system according to claim 1, wherein the aqueous solutionincludes a sodium magnesium as a solute.
 4. The cooling system accordingto claim 1, wherein the aqueous solution includes a sodium calcium as asolute.
 5. The cooling system according to claim 1, further comprising apermeating member for the aqueous solution.
 6. The cooling systemaccording to claim 1, further comprising a sprinkler which sprinkles theaqueous solution.
 7. The cooling system according to claim 1, furthercomprising a ventilator for enhancing the evaporation.
 8. The coolingsystem according to claim 1, further comprising a chimney which is usedfor generating an updraft for enhancing the evaporation.
 9. The coolingsystem according to claim 1, further comprising a dust-preventiondevice.
 10. The cooling system according to claim 1, wherein the waterproviding device is an absorption heat pump which is supplied with theimpurities-containing water and the aqueous solution.
 11. The coolingsystem according to claim 10, further comprising a heating device foroperating absorption heat pump in a high-temperature atmosphere.
 12. Thecooling system according to claim 10, further comprising a vacuum devicefor operating the absorption heat pump in a vacuum atmosphere.
 13. Thecooling system according to claim 1, further comprising a filtrationdevice for removing a solid material contained in theimpurities-containing water.
 14. The cooling system according to claim1, further comprising a water processing device for decomposing anorganic material contained in the impurities-containing water.
 15. Thecooling system according to claim 1, further comprising a distillationdevice having a condensation part, wherein the evaporation coolingdevice is disposed at the condensation part.
 16. The cooling systemaccording to claim 1, wherein the distillation device further includes aheat-absorbing surface for absorbing a thermal energy of the atmosphere.17. The cooling system according to claim 1, wherein the distillationdevice is supplied with a solar thermal energy.
 18. The cooling systemaccording to claim 1, further comprising a steam power generating systemhaving a condenser, wherein the evaporation cooling device is dispose atthe condenser.
 19. The cooling system according to claim 1, furthercomprising an internal combustion engine, wherein the evaporationcooling device is disposed at the internal combustion engine.
 20. Thecooling system according to claim 1, further comprising aair-conditioner having a high temperature heat source, wherein theevaporation cooling device is disposed as the high temperature heatsource.
 21. The cooling system according to claim 20, wherein theevaporation cooling device is plural.
 22. A cooling method, comprising:a step for taking an impurities-containing water; a step for cooling ahigh-temperature body by evaporating water of an aqueous solution whichhas a boiling point higher than that of the impurities-containing water;a step for causing the water vapor evaporated from theimpurities-containing water to be absorbed in the aqueous solution thatis concentrated by the cooling step; a step for sending the aqueoussolution diluted by the absorption step to the cooling step; a step fordraining the impurities-containing water concentrated by the absorptionstep, and a step for preventing an adhesion of dust of the air.
 23. Thecooling system according to claim 22, wherein the absorption step isperformed by an absorption heat pump which is supplied with theimpurities-containing water and the aqueous solution.
 24. The coolingmethod according to claim 23, further comprising a vacuum evacuatingstep for operating the absorption heat pump in a vacuum atmosphere. 25.The cooling system according to claim 22, further comprising a step forventilating an evaporation surface of the aqueous solution.
 26. Thecooling system according to claim 22, further comprising a step forpreventing an adhesion of dust of the air.
 27. The cooling systemaccording to claim 22, wherein a biological propagation prevention agentis added to the aqueous solution.
 28. The cooling system according toclaim 22, further comprising a step for removing a solid materialcontained in the impurities-containing water.
 29. The cooling systemaccording to claim 22, further comprising a step for decomposing anorganic material contained in the impurities-containing water.
 30. Thecooling system according to claim 22, wherein the aqueous solution inthe cooling step flows from a low temperature part of an evaporationsurface of the aqueous solution to a high temperature part.
 31. Acooling system, comprising: an evaporation cooling device forevaporating an aqueous solution having a boiling point higher than thatof an impurities-containing water; a water providing device which causeswater vapor evaporated from the impurities-containing water to beabsorbed in the aqueous solution; a circulation device which circulatesthe aqueous solution between the water providing device and theevaporation cooling device, and a chimney which is used for generatingan updraft for enhancing the evaporation.
 32. A cooling system,comprising: an evaporation cooling device for evaporating an aqueoussolution having a boiling point higher than that of animpurities-containing water; a water providing device which causes watervapor evaporated from the impurities-containing water to be absorbed inthe aqueous solution; a circulation device which circulates the aqueoussolution between the water providing device and the evaporation coolingdevice, and a dust-prevention device.